Grizz 600 clutch/engine noise ???

After a wicked snow ride and all out doughnut run, my buddy’s Grizz started
making a horrible clacking noise. He seem to be low on oil , we added some and decided to further inspect the CVT. I’m not too familiar with the mechanics of the CVT except for how it works or snorkeling it. We didn’t see anything out of place or wrong with the CVT visually, the sound seems to be coming from behind the smaller pulley in the motor. I’m not sure where to go or look/troubleshoot next ?? Any input would be greatly appreciated. Bike still runs and drives .